Drilling operation suspension spool

ABSTRACT

A drilling operation suspension spool system which operates to provide a dual sealing barrier for a well during suspension of drilling operations. The system includes a spool having a spool adapted to be secured in fixed relation to a wellhead and a dummy hanger adapted to be matedly inserted into the spool. The dummy hanger includes an annular sleeve and a removable axial plug disposed within the annular sleeve insert. A plurality of extendable and retractable locking pins secure the dummy hanger in place.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of U.S. Non-Provisional patent application Ser. No. 12/835,349, filed Jul. 13, 2010, which is incorporated by reference herein.

TECHNICAL FIELD

The present invention relates generally to barrier systems for wells, and more particularly, to a barrier system adapted to provide secondary protective sealing for a tubing head operatively engaging an oil or gas well.

BACKGROUND OF THE INVENTION

It is well known to increase production from oil and gas formations by so called “fracturing” to increase the permeability of the production zone. In general, fracturing involves pumping pressurized fluids through perforations in a well casing into a production zone in order to break or fracture pores in the production zone. In the fracturing procedure, fracturing fluids are pumped under very high pressures of about 5,000 to 10,000 psi through the perforations into the formation. The high pressure breaks the formation to form flow channels for hydrocarbon fluids. In practice, it is common to carry out fracturing procedures for a collective group of wells and to then seal some or all of those wells for a period of time until production operations commence.

Oil and gas wells are typically provided with a production tubing head (also known as a tubing spool) which serves as a connection for the fracturing equipment as well as for the introduction tubing or other equipment into the well interior during production. As will be appreciated, following the fracturing operation, the well typically has a substantial positive pressure as hydrocarbons seek to exit from the production zone. Once the fracturing equipment is removed, it is therefore necessary to seal off the tubing head to avoid backflow from the well and to avoid the introduction of debris into the tubing head. As part of this sealing procedure, it is common to introduce a tubing hanger into the axial bore of the tubing head to provide an axial seal.

The use of such tubing hangers is considered generally desirable due to the ease of use and ability to maintain full bore access by removing the hanger. However, it has been found that tubing hangers may be susceptible to damage and/or may permit a pressure leak when subjected to high pressure over extended periods following the fracturing operation. Accordingly, a supplemental tubing head barrier that may be adapted to function with existing tubing head constructions to provide additional sealing protection without unduly limiting access to the tubing head interior would be desirable.

SUMMARY OF THE INVENTION

The present invention provides advantages and alternatives over the prior art by providing a spool in the form of an adapter which operates to provide a supplemental sealing barrier for a wellhead during suspension of drilling operations while maintaining access to the interior of the wellhead. The present invention also provides a dual barrier stack-up completion that allows removal of the fracture stack and production tree installation with dual barriers between produced hydrocarbons and the atmosphere.

In accordance with one aspect, the present invention provides spool for disposition in sealing relation to a wellhead operatively connected to a hydrocarbon well. The spool includes an annular body adapted to be secured in fixed relation to the wellhead. The annular body includes an axial channel, a first set of radial locking pin channels extending radially away from the axial channel and at least a second set of radial locking pin channels extending radially away from the axial channel. The second set of radial locking pin channels are axially spaced from the first set of radial locking pin channels. A dummy hanger is adapted to be matedly inserted into the axial channel. The dummy hanger includes an annular sleeve insert having a central bore and a removable axial plug disposed within the central bore. The annular sleeve insert includes a plurality of pin receiving channels extending radially through the annular sleeve insert for aligned relation with the first set of radial locking pin channels. A first set of extendable and retractable locking pins are disposed within the first set of radial locking pin channels. The first set of extendable and retractable locking pins includes distal ends adapted to project through the pin receiving channels in the annular sleeve insert to engage the axial plug. A second set of extendable and retractable locking pins are disposed within the second set of radial locking pin channels. The second set of extendable and retractable locking pins include distal ends adapted to engage the annular sleeve insert. A first compressible seal is disposed circumferentially about the annular sleeve insert. At least a second compressible seal is disposed circumferentially about the annular sleeve insert in axially spaced relation from the first compressible seal. At least a third compressible seal is disposed circumferentially about the axial plug. At least a fourth compressible seal is disposed circumferentially about the axial plug in axially spaced relation from the third compressible seal.

In accordance with another aspect, the invention provides another drilling operation suspension spool system for disposition in sealing relation to a wellhead operatively connected to a well. The spool system includes a spool with an annular body adapted to be secured in fixed relation to the wellhead and including an axial channel. The annular body includes an upper, middle and lower set of radial locking pin channels extending radially away from the axial channel and being axially spaced apart. A dummy hanger is adapted to be matedly inserted into the axial channel and includes an annular sleeve insert having a central bore and a removable axial plug disposed within the central bore of the annular sleeve insert. The annular sleeve insert includes a locking groove for aligned relation with the middle set of radial locking pin channels. An upper set of extendable and retractable locking pins are disposed within the upper set of radial locking pin channels. The upper set of locking pins include distal ends adapted to project to a position radially inward of the central bore of the annular sleeve insert so as to limit upward axial movement of the axial plug. A middle set of extendable and retractable locking pins is disposed within the middle set of radial locking pin channels and includes distal ends adapted to engage the locking groove of the annular sleeve insert. A further lower set of extendable and retractable locking pins is disposed within the lower set of radial locking pin channels and include distal ends adapted to project to a position radially inward of the central bore of the annular sleeve insert. First and second compressible seals are disposed circumferentially about the annular sleeve insert in axially spaced apart relation. Third and fourth compressible seals are disposed circumferentially about the axial plug and in axially spaced relation.

Other exemplary constructions, features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of an exemplary tubing head with a tubing hanger in place and with an exemplary sealing adaptor consistent with the present disclosure in place across the tubing head with a dummy hanger sleeve and axial plug removed;

FIG. 2 is a side sectional view of the exemplary sealing adapter of FIG. 1 showing the dummy hanger annular sleeve insert and axial plug in place;

FIG. 3 is a sectional plan view taken generally through line 3-3 in FIG. 1 showing an exemplary positional arrangement for locator pins and locking pins holding the dummy hanger annular sleeve insert and axial plug in place;

FIG. 4 is a side sectional view of an alternative embodiment of the invention providing a unibody tubing head and sealing adaptor with a tubing hanger in place in the tubing head portion with a dummy hanger sleeve and axial plug removed; and

FIG. 5 is a side sectional view of another embodiment of the invention with a drilling operation suspension spool in place on a wellhead.

Before the embodiments of the invention are explained in detail, it is to be understood that the invention is in no way limited in its application to the details of construction and/or to the arrangements of the components set forth in the following description or illustrated in the drawings. Rather, the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for purposes of description only and should not be regarded as limiting. The use herein of “including”, “comprising”, and variations thereof is meant to encompass the items listed thereafter and equivalents, as well as additional items and equivalents thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings. To the extent possible, like elements are designated by like reference numerals in the various views. Referring to FIG. 1, a wellhead in the form of a production tubing head 12 (also referred to as a tubing spool) is shown with a tubing hanger 14 in place within the axial bore 16 of the tubing head 12. In practice, the tubing head 12 is operatively connected to a well casing (not shown) in a manner as will be well known to those of skill in the art. As shown, the tubing head 12 may include a connection leg 18 for attachment of fracturing equipment or the like. In the illustrated exemplary arrangement, the connection leg 18 may be sealed by use of an isolation valve 20 and a flange seal 22. Thus, the tubing hanger 14 in combination with the isolation valve 20 and the flange seal 22 act to provide primary sealing of the production tubing head 12. However, other primary sealing arrangements may be used if desired.

In a typical arrangement, the production tubing head 12 has a circular spool shape and includes a lower attachment flange 26 as well as an upper attachment flange 28. As will be appreciated, the lower attachment flange 26 and the upper attachment flange 28 each typically includes a multiplicity of bolt holes arranged circumferentially about the perimeter outboard from the axial bore 16. Connection bolts may be run through the bolt holes to permit attachment of other structures at either end of the production tubing head 12.

In accordance with the present invention, a spool in the form of a sealing adapter 30 may be operatively connected across the upper attachment flange 28 to allow for the suspension of drilling operations. As will be described further hereinafter, the sealing adapter 30 acts to provide a secondary sealing barrier for the production tubing head 12 when fracturing operations are complete. The sealing adapter 30 also provides protection for the tubing hanger 14.

Referring now jointly to FIGS. 1-3, in the illustrated exemplary embodiment, the sealing adapter 30 includes an annular body 32 which may be mounted in fixed relation across the upper attachment flange 28 of the production tubing head 12 by use of attachment bolts 34 (FIG. 2) extending downwardly for engagement with complementary bolt holes arranged circumferentially about the upper attachment flange 28. By way of example only, and not limitation, the annular body 32 may be formed from cast steel or other suitable metal, although non-metallic materials may also be used if desired. As shown, the annular body 32 may be secured in place by nuts 36 which engage the attachment bolts 34. In this regard, it will be understood that in actual practice attachment bolts 34 typically will be disposed circumferentially about the annular body 32 for connection using complementary nuts. By way of example only, and not limitation, one such exemplary pattern is illustrated in FIG. 3. However, it is likewise contemplated that a larger or smaller number of bolt positions may be used if desired. As illustrated, attachment bolts 34 may also extend outwardly from an upper surface of the annular body 32 for attachment to additional structures (not shown).

As illustrated, the annular body 32 includes an axial channel 40 for disposition in substantial alignment with the axial bore 16 of the production tubing head 12. Thus, the neck of the tubing hanger 14 may project upwardly into the axial channel 40. As best seen through joint reference to FIGS. 2 and 3, the annular body 32 also includes an arrangement of radial channels for mounting extendable and retractable pins. In this regard, a first radial locator channel 42 and a second radial locator channel 44 are disposed in opposing relation to one another on either side of the axial channel 40. The first radial locator channel 42 is adapted to hold a first locator pin 46 which may be extended and retracted radially relative to the axial channel 40. The second radial locator channel 44 is adapted to hold a second locator pin 48 which also may be extended and retracted radially relative to the axial channel 40. As shown in FIG. 2, the second locator pin 48 is longer than the first locator pin 46.

In the illustrated exemplary arrangement, the annular body 32 further includes a first set of radial locking pin channels 50 which are adapted to hold a first set of locking pins 52 which may be extended and retracted radially relative to the axial channel 40. In the illustrated exemplary arrangement, the annular body 32 further includes a second set of radial locking pin channels 56 which are adapted to hold a second set of locking pins 58 which may be extended and retracted radially relative to the axial channel 40. In the illustrated exemplary configuration the first set of locking pins 52 are longer and thinner than the second set of locking pins 58.

FIG. 3 illustrates one exemplary pattern for placement of the locator pins 46, 48 and the first set of locking pins 52 around the circumference of the annular body 32. In this exemplary arrangement, the individual locking pins 52 are arranged at positions between the locations of the attachment bolts 34. The second set of locking pins 58 may be arranged in substantially the same pattern as the first set of locking pins 52. However, other positional arrangements may be used if desired such that the first set of locking pins 52 may be offset from the second set of locking pins 58 if desired.

As shown, the sealing adapter 30 includes a dummy hanger designated generally as 60 adapted for sliding insertion into the axial channel 40. In the illustrated exemplary construction the dummy hanger 60 includes an annular sleeve insert 62 and an axial plug 64 of substantially solid construction which is matedly inserted into the interior bore of the annular sleeve insert 62. Both the annular sleeve insert 62 and the axial plug 64 may be formed from a steel alloy or other suitable material as may be desired.

As best seen in FIG. 2, in the exemplary embodiment the lower edge of the annular sleeve insert includes a first positioning notch 66 which is configured to accept the distal end of the first locator pin 46 when the first locator pin 46 is in an inserted condition. Thus, by advancing the first locator pin 46 into the axial channel 40 and then inserting the annular sleeve insert 62, both the height and rotational orientation of the annular sleeve insert 62 are established. In this regard, it will be understood that the width of the first positioning notch 66 preferably closely matches the distal end of the first locator pin 46 to prevent substantial rotational movement following initial placement. Likewise, the outer diameter of the annular sleeve insert 62 preferably matches closely with the inner diameter of the axial channel 40 to prevent the annular sleeve insert from tilting within the axial channel 40.

As shown, the annular sleeve insert 62 includes a reduced diameter neck 68 which extends circumferentially about the annular sleeve insert 62. As best seen in FIG. 2, the reduced diameter neck 68 is positioned to engage distal ends of the upper locking pins 58 when the annular sleeve insert has engaged the first locator pin 46 and the upper locking pins have been advanced into the axial channel 40. Thus, by advancing the upper locking pins 58, the annular sleeve insert may be locked in place against axial withdrawal.

As shown, the annular sleeve insert 62 further includes a number of pin receiving channels 65 which are oriented to be in substantial alignment with the first set of radial locking pin channels 50. Thus, distal ends of the lower locking pins 52 may project through the pin receiving channels 65 to engage the exterior of the axial plug 64. Thus, by advancing the lower locking pins 52, the axial plug 64 may be locked in place against axial withdrawal.

The annular sleeve insert 62 and the axial plug 64 cooperatively form a double barrier seal relative to the tubing hanger 14 and the operatively connected production tubing head 12. In this regard, in the illustrated exemplary construction the annular sleeve insert 62 includes a pair of circumferential grooves 70 which are adapted to hold a first set of o-rings 72 or other compressible seals. As will be appreciated, the o-rings 72 provide a tight seal between the annular sleeve insert 62 and the inner wall of the annular body 32. In this regard, the o-rings 72 are spaced apart from one another along the height of the annular sleeve insert 62 to provide a double seal relationship. Thus, even if one seal fails, the overall sealing relation nonetheless remains intact.

As noted previously, the axial plug 64 is configured to be slidingly inserted into the interior bore of the annular sleeve insert 62. Alternatively, rather than use the axial plug 64, the user can adapt a type H back pressure valve that is threadingly inserted into the sleeve 62. The fullbore back pressure valve axial plug 64 allows the use of a production tree that matches the bore of the tubing used in the completion. For instance, where a type H back pressure valve is used in the lower hanger and a 2″ full bore axial plug 64 is used in the upper hanger, a 2 1/16″ bore production tree can be installed on the well. In this example, when a type H back pressure valve is used in both the upper and lower hanger, a 2″ back pressure valve is used in the lower hanger and a 2½″ back pressure value is used in the upper hanger. This installation would then require the use of a larger 2 9/16″ bore production tree. As best seen in FIG. 2, in the exemplary embodiment the lower edge of the axial plug 64 includes a second positioning notch 76 which is configured to accept the distal end of the second locator pin 48 when the second locator pin 48 is in an inserted condition. When the annular sleeve insert 62 is oriented such that the first locator pin engages the first positioning notch 66, the second locator pin 48 will be aligned with a radial positioning channel 78 in the wall of the annular sleeve insert 62. Thus, once the annular sleeve insert 62 is in place, the second locator pin 48 may be advanced through the radial positioning channel 78 to project into the inner bore of the annular sleeve insert. Accordingly, by first advancing the second locator pin 48 to the position illustrated in FIG. 2, and then inserting the axial plug 64, both the height and orientation of the axial plug 64 are established within the inner bore of the annular sleeve insert 62. As will be appreciated, the width of the second positioning notch 76 preferably closely matches the distal end of the second locator pin 48 to prevent substantial rotational movement following initial placement. In addition, the outer diameter of the axial plug 64 preferably matches closely with the inner diameter of the annular sleeve insert 62 to prevent the axial plug 64 from tilting within the annular sleeve insert 62.

In the illustrated exemplary construction, the axial plug 64 includes a pair of circumferential grooves which are adapted to hold a second set of o-rings 80 or other compressible seals. As will be appreciated, the second set of o-rings 80 provides a tight seal between the axial plug 64 and the inner wall of the annular sleeve insert 62. In this regard, the o-rings 80 are spaced apart from one another along the height of the axial plug 64 to provide a double seal relationship. Thus, even if one seal fails, the overall sealing relation between the axial plug 64 and the annular sleeve insert remains intact.

As shown, in the exemplary configuration the first set of o-rings 72 is oriented in staggered relation to the second set of o-rings 80 such that each o-ring is at a different height within the sealing adapter 30. Such an arrangement may aid in the efficacy of the overall sealing relation.

In at least one exemplary embodiment, one or more testing ports may extend through the annular body 32. These testing ports are arranged at different heights along the sealing adapter 30 to permit monitoring of performance at different locations. By way of example only, in the illustrated exemplary embodiment a first testing port 82 is positioned at a height between the tubing hanger 14 and the bottom of the dummy hanger 60. As will be appreciated, the sealing performance of the tubing hanger 14 can be monitored at the first testing port 82. A second testing port 84 is positioned at a height between the upper and lower members of the first set of o-rings 72. As will be appreciated, by monitoring the pressure at the second testing port 84, the performance of the seals formed by the lower o-rings 72 can be evaluated. A third testing port 86 is positioned at a height above the seals and the reduced diameter neck 68 on the annular sleeve insert 62. Thus, by monitoring the pressure at the third testing port 86, the overall sealing performance of the sealing adapter may be evaluated. Moreover, in the event that a proper sealing relation is not being achieved, the positions of the various testing ports permit a user to diagnose the location where the sealing function has failed.

In practice, the annular body 32 may be installed across the production tubing head 12 before fracturing operations take place. After installation of the tubing hanger 14, the system may be pressure tested using the first testing port 82 to confirm proper sealing. The first locator pin 46 may then be extended such that the distal end projects into the axial channel 40. With the first locator pin 46 in the extended position, the annular sleeve insert 62 is then inserted in substantially coaxial relation with the annular body 32 and with the first positioning notch 66 fitting about the distal end of the first locator pin 46. The height and rotational relation of the annular body 32 is thus established. The second set of locking pins 58 may then be advanced to engage the reduced diameter neck 68 to lock the annular sleeve insert 62 in place. A pressure test may then be performed through the second testing port 84.

Once the annular sleeve insert 62 is properly positioned, the second locator pin 48 may be advanced through the radial positioning channel 78 in the annular sleeve insert 62 such that the distal end of the second locator pin 48 extends into the bore of the annular sleeve insert 62. With the second locator pin 48 in the extended position, the solid axial plug 64 may be inserted in substantially coaxial relation with the annular body 32 and annular sleeve insert 62 and with the second positioning notch 76 fitting about the distal end of the second locator pin 48. The height and rotational relation of the axial plug 64 is thus established. The first set of locking pins 52 may then be advanced to lock the axial plug 64 in place. A pressure test may then be performed through the third testing port 86 to confirm the overall sealing function.

In use, the sealing adapter 30 provides an effective second barrier across the production tubing head 12 once fracturing operations are complete and the fracturing equipment has been removed. In particular, the sealing adapter 30 acts to protect the neck of the tubing hanger 14 or other primary sealing device while nonetheless providing access by removal of the solid axial plug 64.

As seen in an alternative embodiment in FIG. 4, the tubing head 12 and sealing adaptor 30 may be forged from a single piece rather than connecting the sealing adaptor 30 to the tubing head In this embodiment, it will be readily understood that the attachment bolts 34 and nuts 36 are no longer required. Other than being formed from a single piece rather than separate tubing head and sealing adaptor, the operation of this embodiment is the same as that of the embodiment shown in FIGS. 1 through 3.

Another embodiment of a drilling operation suspension spool system is shown in FIG. 5. The features of the embodiment shown in FIG. 5 may be combined with those features of the embodiments shown in FIGS. 1-4. Further, particular details have been omitted from the drawing shown in FIG. 5, and it should be understood that the description provided above with respect to the embodiment of FIGS. 1-4 of these features applies to the embodiment of FIG. 5, for example, the position of the testing ports or the configuration of the pins or bolts.

FIG. 5 shows an upper part of a wellhead 112 having an axial bore 116 and an upper flange 128 including bolt holes having any number of configurations, as set forth above. The upper flange 128 is configured for connecting with additional structure to the wellhead, such as the drilling operations suspension spool described further below. The wellhead 112 may include a connection leg 118 which could be used for attachment of additional equipment, e.g., fracturing equipment, and may include a valve 120 for sealing the connection leg. A casing hanger with a false bowl 114 is disposed in the axial bore 116 of the wellhead 112. The false bowl 114 can retain a lower plug 122 or test plug, with O-rings providing a seal between the plug and the false bowl 114. An inner diameter 124 can house a solid plug 126 or a back pressure valve.

The drilling operations suspension spool 130 can be operatively connected to the upper flange 128 of the wellhead using a number of bolts, with one of various possible configurations, as set forth above with respect to the previously described embodiments. The spool 130 includes an annular body 132 that is fixed on the flange 128 of the wellhead with seal rings 134 disposed between the facing surfaces of the wellhead flange 128 and the annular body 132. Additional structures can be attached above the operation suspensions spool 130 using additional bolts and another seal ring 134. In the illustrated embodiment, a simple flange, or nightcap 136 is provided above the operations suspension spool.

As shown in the drawings, the annular body 132 of the operations suspension spool 130 includes an axial channel 140 that is aligned with the axial bore 116 of the wellhead 112. Similar to the embodiments of FIGS. 1-4, several sets of radial channels 142, 144, 146 extend through the annular body 132. In the cross-section depiction of FIG. 5, only two channels are shown on each side of the annular body 132, however it should be understood that an arrangement of channels can be provided around the circumference of the axial channel 140. Each set of radial channels 142, 144, 146 holds a corresponding set of locking pins 152, 154, 156 for positional locking of components disposed within the axial channel 140.

The system for providing suspension of drilling operations includes a dummy hanger 160 having the combination of an upper test plug 162 surrounded by an annular bowl adapter sleeve 164 installed around the upper plug 162. The sleeve 164 includes an outer surface 170 that is sized to functionally mate with the inner surface of the axial channel 140. Within a central bore 150 of the sleeve 164, the plug 162 has a mating surface 148 that mates with the bore 150. While the mating surface 148 of the illustrated plug 162 is shown as the outermost surface, it is not necessary that the mating surface 148 be at outer extent of the plug. For example, the plug 162 could extend above the sleeve 164, where the outer diameter could increase to a diameter larger than the central bore 150 of the sleeve.

Two seals 166 are provided between the upper plug 162 and sleeve 164 in axially spaced relation. As a result, the failure of one of the two seals 166 will not result in absolute failure of the sealing provided by drilling operation suspension spool. This dual sealing is also provided by two seals 168 disposed between the sleeve 164 and annular body 132 of the spool 130 in axially spaced relation. As a result, each of the paths between the wellhead and the atmosphere that pass through spool 130 are closed by two separate seals. In this regard, high pressures resulting from released hydrocarbons can be adequately contained within the well. In the embodiment shown in FIG. 5, each of the seals 166, 168 is provided by an O-ring. The plug 162 includes upper and lower grooves for holding the O-rings 166 between the outer circumferential mating surface 148 of the plug 162 and the inner surface of the sleeve. Likewise, the outer surface of the sleeve includes upper and lower grooves for holding the O-rings 168 between the sleeve 164 and the annular body 132 of the drilling operations suspension spool 130. Alternatively, the grooves housing the O-rings 166, 168 could be on the inner surface of the sleeve 164 and annular body 132, respectively, or the seals could be provided by an entirely different means. As can be seen in FIG. 5, the upper O-ring 166 is not axially aligned with upper O-ring 168, whereas the lower O-rings 166, 168 are substantially aligned. It should be understood that configurations where none of the seals 166, 168 are aligned, where the upper and lower seals are aligned, or where the upper seal 166 of one set is aligned with the lower seal 168 of the other set, or vice versa.

The locking pin sets 152, 154, 156 respectively disposed in radial pin channels 142, 144, 146 are used to fix the position of the dummy hanger 160 and false bowl 114 by extending and retracting within the channels. Specifically, the middle set of locking pins 154 can extend radially inward so that the distal end of each pin engages with one or more locking engagement groove 158 disposed around the circumference of the sleeve 164. The locking engagement groove 158 is shown as a circumferential groove or narrow neck portion of the sleeve 164. However, the engagement could alternatively include a plurality of notches configured to receive each pin of the middle set 154 individually. Further, the locking engagement groove 158, as shown, is disposed at a central location between the upper and lower seals 168. Alternatively, both of the upper and lower seals 166 could be disposed on one side of the locking engagement groove 158. In use, the middle set 154 of locking pins is extended to the radially inward position when the sleeve is in place within the spool 130 in order to lock the sleeve in place.

Due to the tightly sealed fit between the sleeve 164 and the upper plug 162, the plug can be inserted into the spool 130 in an assembly with the sleeve. Further, the plug 162 will be held fixed within the sleeve 164, to a limited extent, by the seal itself. However, to account for potential pressure within the well resulting from the release of high pressure hydrocarbons, the plug must be fixedly held by more reliable means. Accordingly, the upper set of pins 152 can extend radially inward through the channel 142 to such an extent that the distal ends of the upper pins are disposed radially inward of the central bore 150 of the outer sleeve 164. As a result, the circumferential surface 148, which has a size corresponding to central bore 150 is unable to move past the extended pins of set 152. Thus, the positioning of the extended pins 152 prevents the upper plug from becoming dislodged and forced upward, even under high pressure from within the well. In the illustrated embodiment, the upper end of plug 162 includes a chamfered edge that engages with a distal tip of the pins. Alternatively, a simpler construction with a flat upper surface of plug 162 is also possible. Moreover, the plug could include radial bores configured to receive pins 152 similar to the embodiment shown in FIGS. 1-4. In order to remove plug 162 the upper set of pins 152 can be refracted into the corresponding channels 142 so as to release the limit of movement of the plug. The plug 162 can then be removed from the sleeve 164. Alternatively, if both the upper set and middle set of pins 152, 154 were retracted into to the channels 142, 144, the sleeve and plug could be removed as a unit.

Similar to the upper set of pins, the lower set of pins 156 can extend radially to a position inward of the central bore 150 of sleeve 164. Due to the relationship of the size of the central bore 150 and the size of the circumferential surface of upper plug 162, this inward position of pins 156 technically limits the downward movement of the plug 162. However, such downward movement is unlikely, as pressure forces are expected within the well, thereby forcing the plugs upward. Advantageously, the pins 156 also limit upward movement of the hanger and false bowl 114 disposed in the wellhead 112. Depending on the size of the hanger disposed in the wellhead, the extent to which the lower pins 156 extend inward may vary, and the distal ends of the pins may extend to a diameter that is smaller or larger than the diameter to which the distal end of upper pins 152 extends. Furthermore, it is possible that the lower set of pins can be eliminated entirely, if the containment of structures within the wellhead is unnecessary. Similar to upper plug 162, the false bowl 114 can include a chamfered edge at the top surface thereof to engage with the distal ends of the lower pins 156, which may be conical. Alternatively, the pins 156 and the false bowl 114 can have an alternative geometry.

A method of using a drilling operation suspension spool in accordance with an embodiment of the present invention will be discussed in the following with reference to the embodiment of the spool that is shown in FIG. 5.

The drilling operation suspension spool provides sealing, for example, in a situation in which it is desirable to continue air drilling beyond the surface pipe shoe, and subsequently suspend drilling operations. Conventionally, the suspension of drilling operations could be expensive and costly once the surface pipe shoe has been drilled out. However, the suspension spool of the present invention provides dual sealing of the well, which allows the drilling operation to be suspended safely, effectively and at a reasonable cost.

The suspension spool 130 is installed on a previously installed wellhead, such as conductor multibowl wellhead 112 shown in FIG. 5. Additional structure for drilling operations, such as a diverter preventer is installed on top of spool 130 for conducting drilling operations. For example, before proceeding with drilling operations, such as air drilling, the false bowl type casing hanger 114 is landed through the diverter in the wellhead housing 112. The drilling rig can then pick up the bottom hole assembly (BHA) and continue drilling operations until the total depth is reached just above the desired formation such as the Marcellus shale. After the drilling operations, the hole is filled with a drilling mud, such as synthetic oil based mud, and the drilling rig is removed.

After the completion of drilling, operations are suspended by sealing the hole. Initially, the lower test plug 122 is installed in the false bowl 114. To lock the lower test plug 122 in place, the lower pins 156, which are disposed at an axial height corresponding to the top end of the lower test plug 122 are extended, so that the distal ends of lower pins 156 engage the top of test plug 122. As a result, the lower test plug is securely fixed within the false bowl 114 of the hanger. The upper plug 162 and annular bowl adapter sleeve 164 are then landed, through the diverter preventer, within the operation suspension spool 130. Conveniently, the plug 162 and sleeve 164 can be installed together, though it is also possible for the plug 162 to be inserted in the sleeve 164 after the sleeve is installed.

As an example of possible dimensional relationships for the parts used in the drilling operation, the wellhead 112 includes a 13⅝″ multibowl housing and the hanger/false bowl installed in the wellhead 112 includes a 9⅝″ hanger with a 10¾″ bowl. The drilling operation suspension spool can also include a axial channel of 13⅝″. Likewise the drilling operating structure disposed above the operations, can be similarly sized, such as a 13⅝″ diverter preventer. Thus, the false bowl and hanger 114, can be installed through the diverter preventer. The sleeve 164 is a 13⅜″×10 3/4″ bowl disposed around a 10¾″ plug that forms the upper test plug 162. The lower test plug 122 has a similar diameter.

Once the upper plug 162 and annular sleeve 164 are disposed within spool 130, the middle set of pins 154 are extended radially inward to engage with locking engagement 158 of the sleeve 164. The sleeve is consequently axially locked in place within spool 130. To further lock the upper plug 162 within the sleeve 164, the upper pins 152 may then be radially extended inward until the inner distal ends of the pins pass the circumferential surface of upper plug 162 that fits within central bore 150 of sleeve 164. Thereby, the upper pins 152 prevent axial movement of upper plug 162. In the installed position, with the upper plug 162 and sleeve 164 disposed in the spool 130, the seals are tested using test ports. With verification that the double seals are reliable, the drilling operations can be suspended.

At this stage, any structure disposed on spool 130 used for drilling operations, such as the 13⅝″ diverter, can be disassembled or “nippled down.” In its place, a simple flange or nightcap 136 is installed on the spool 130 while operations are suspended. The drilling rig can then move on to a new pad.

Subsequently, drilling operations can commence according to the schedule of a hydraulic drilling rig for drilling out one or more horizontal hole sections. The hydraulic rig is moved into place and the nightcap flange is removed. A blowout preventer (BOP) is then assembled, or nippled up, on the spool 130. In the described embodiment, an 11″ BOP is used. The BOP can then be tested against the plugs disposed in the spool 130, which have already been proven. After testing of the BOP is completed, the drill pipe is screwed into the upper plug 162 and the upper pins 152 are axially retracted into upper channels 142, thereby releasing the upper plug 162. With the annular sleeve 164 held in place within spool 130 by the middle pins 154, the upper plug 162 is removed by the drilling pipe through the BOP. Further, the lower plug 122 is subsequently removed through the annular sleeve 164 and BOP.

At this point, drilling operations may commence, in which the horizontal leg (or legs) is drilled to total depth and casing such as 5½″ casing is ran and cemented. A casing hanger such as 10¾″×5½″ casing hanger is installed and the corresponding seals are confirmed. The BOP and drilling operation suspension spool can each now be nippled down and the drilling rig released. The well is now ready for installation of a tubing spool, after which fracturing, flowback and completion operations can proceed.

Of course, variations and modifications of the foregoing are within the scope of the present invention. Thus, it is to be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the invention. The embodiment described herein explain the best modes for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments and equivalents to the extent permitted by the prior art.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Various features of the invention are set forth in the following claims. 

1. A drilling operation suspension spool system for disposition in sealing relation to a wellhead operatively connected to a well, the spool system comprising: a spool adapted to be secured in fixed relation to the wellhead, the spool including an axial channel, an upper set of radial locking pin channels extending radially away from the axial channel, a middle set of radial locking pin channels extending radially away from the axial channel, and a lower set of radial locking pin channels extending radially away from the axial channel, the upper, middle and lower sets of radial locking pin channels being axially spaced apart; a dummy hanger adapted to be matedly inserted into the axial channel, the dummy hanger including an annular sleeve insert having a central bore and a removable axial plug disposed within the central bore of the annular sleeve, the annular sleeve including a locking engagement for aligned relation with the middle set of radial locking pin channels; an upper set of extendable and retractable locking pins disposed within the upper set of radial locking pin channels, the upper set of extendable and retractable locking pins including distal ends adapted to project to a position radially inward of the central bore of the annular sleeve insert so as to limit upward axial movement of the axial plug; a middle set of extendable and retractable locking pins disposed within the middle set of radial locking pin channels, the middle set of extendable and retractable locking pins including distal ends adapted to engage the locking engagement of the annular sleeve; a lower set of extendable and retractable locking pins disposed within the lower set of radial locking pin channels, the lower set of extendable and retractable locking pins including distal ends adapted to project to a position radially inward of the central bore of the annular sleeve; a first compressible seal disposed circumferentially about the annular sleeve; a second compressible seal disposed circumferentially about the annular sleeve in axially spaced relation from the first compressible seal; a third compressible seal disposed circumferentially about the axial plug; and a fourth compressible seal disposed circumferentially about the axial plug in axially spaced relation from the third compressible seal.
 2. The drilling operation suspension spool system as recited in claim 1, wherein the removable axial plug includes a circumferential surface that is slidably inserted in the central bore the annular sleeve.
 3. The drilling operation suspension spool system as recited in claim 1, wherein the locking engagement of the annular sleeve includes a groove, and wherein the distal ends of the middle pins are configured to engage the locking engagement by insertion into the groove.
 4. The drilling operation suspension spool system as recited in claim 1, wherein an axial distance between the upper and lower sets of locking pins is substantially equal to an axial height of the annular sleeve.
 5. The drilling operation suspension spool system as recited in claim 1, wherein the first and second compressible seals are sealed against each of the annular sleeve and the axial channel of the spool.
 6. The drilling operation suspension spool system as recited in claim 1, wherein the third and fourth compressible seals are sealed against each of the central bore of the annular sleeve and the mating surface of the removable axial plug.
 7. The drilling operation suspension spool system as recited in claim 1, wherein the upper set of extendable and retractable locking pins is disposed above the annular sleeve and the lower set of extendable and retractable pins is disposed below the annular sleeve.
 8. A drilling operation suspension spool system for disposition in sealing relation to a wellhead operatively connected to a hydrocarbon well, the spool system comprising: a spool adapted to be secured in fixed relation to the wellhead, the spool including an axial channel, a first set of radial locking pin channels extending radially away from the axial channel, and a second set of radial locking pin channels extending radially away from the axial channel, the first and second sets of radial locking pin channels being axially spaced apart; a dummy hanger adapted to be matily inserted into the axial channel, the dummy hanger including an annular sleeve insert having a central bore and a removable axial plug having a mating surface, the axial plug being disposed within the central bore of the annular sleeve insert with the mating surface adjacent the central bore, the annular sleeve insert including a locking engagement for aligned relation with the second set of radial locking pin channels; a first set of extendable and retractable locking pins disposed within the first set of radial locking pin channels, the first set of extendable and retractable locking pins including distal ends adapted to project to a position radially inward of the mating surface of the axial plug so as to limit axial movement of the axial plug; a second set of extendable and retractable locking pins disposed within the second set of radial locking pin channels, the second set of extendable and retractable locking pins including distal ends adapted to engage the annular sleeve insert; a first compressible seal disposed circumferentially about the annular sleeve insert; a second compressible seal disposed circumferentially about the annular sleeve insert in axially spaced relation from the first compressible seal; a third compressible seal disposed circumferentially about the axial plug; and a fourth compressible seal disposed circumferentially about the axial plug in axially spaced relation from the third compressible seal.
 9. The drilling operation suspension spool system as recited in claim 8, wherein the first set of extendable and retractable locking pins is disposed at a position so as to engage an upper end of axial plug and prevent upward movement of the axial plug.
 10. The drilling operation suspension spool system as recited in claim 8, wherein the first set of extendable and retractable locking pins is axially disposed above the annular sleeve.
 11. The drilling operation suspension spool system as recited in claim 8, wherein the first and second compressible seals are sealed against each of the annular sleeve and the axial channel of the spool, and the third and fourth compressible seals are sealed against each of the central bore of the annular sleeve and the mating surface of the removable axial plug.
 12. The drilling operation suspension spool system as recited in claim 8, wherein the removable axial plug includes a circumferential surface that is slidably inserted in the central bore the annular sleeve.
 13. The drilling operation suspension spool system as recited in claim 8, wherein the locking engagement of the annular sleeve includes a groove, and wherein the distal ends of the middle pins are configured to engage the locking engagement by insertion into the groove.
 14. A method of providing a dual seal across a wellhead operatively connected to a hydrocarbon well during suspension drilling operations, the method comprising: providing a wellhead; attaching a drilling operation suspension spool on the wellhead, the spool including an axial channel, a first set of radial locking pin channels extending radially away from the axial channel, a first set of extendable and retractable locking pins disposed within the first set of radial locking pin channels, a second set of radial locking pin channels extending radially away from the axial channel, and a second set of extendable and retractable locking pins disposed within the second set of radial locking pin channels, the first and second sets of radial locking pin channels being axially spaced apart; landing a dummy hanger in the axial channel of the spool, the dummy hanger including an annular sleeve insert having a central bore and a removable axial plug having a mating surface, the axial plug being disposed within the central bore of the annular sleeve insert with the mating surface adjacent the central bore, the annular sleeve insert including a locking engagement for aligned relation with the second set of radial locking pin channels; providing a first compressible seal disposed circumferentially about the annular sleeve insert, a second compressible seal disposed circumferentially about the annular sleeve insert in axially spaced relation from the first compressible seal, a third compressible seal disposed circumferentially about the axial plug, and a fourth compressible seal disposed circumferentially about the axial plug in axially spaced relation from the third compressible seal; extending the second set of locking pins into the axial channel of spool so as to engage the locking engagement of the annular sleeve and fix the annular sleeve within the spool; and extending the first set of locking pins into the axial channel of the spool so as to position distal ends of the first set locking pins at a position radially inward of the mating surface of the axial plug so as to limit axial movement of the axial plug.
 15. The method as recited in claim 14, further comprising inserting an annular bowl in a housing of the wellhead before landing the dummy hanger in the axial channel of the spool.
 16. The method as recited in claim 15, further comprising inserting a lower plug in the annular bowl before landing the dummy hanger in the axial channel of the spool.
 17. The method as recited in claim 16, further comprising retracting the second set locking pins from the axial channel and from engagement with the annular sleeve into the second set of radial locking pin channels.
 18. The method as recited in claim 17, further comprising removing the axial plug from the annular sleeve.
 19. The method as recited in claim 18, further comprising removing the lower plug from the annular bowl through the annular sleeve. 